Production method of multilayer ceramic electronic device

ABSTRACT

A method of producing a multilayer ceramic electronic device, having a firing step for firing a pre-firing element body wherein a plurality of dielectric layers and internal electrode layers containing a base metal are alternately arranged, characterized in that the firing step has a temperature raising step for raising a temperature to a firing temperature, and hydrogen is continued to be introduced from a point in time of the temperature raising step. According to the method, it is possible to provide a method of producing a multilayer ceramic electronic device, such as a multilayer ceramic capacitor, wherein shape anisotropy and other structural defaults are hard to occur and electric characteristics are improved while suppressing deterioration thereof even if dielectric layers becomes thinner and stacked more.

This is a Continuation of application Ser. No. 10/296,993 now U.S. Pat.No. 7,276,130 filed Dec. 2, 2002 which is a National Stage ofPCT/JP/02/03657 filed Apr. 12, 2002. The disclosures of the priorapplications are hereby incorporated by reference herein in theirentirety.

TECHNICAL FIELD

The present invention relates to a method of producing a multilayerceramic electronic device, such as a multilayer ceramic capacitor.

BACKGROUND ART

A multilayer ceramic capacitor as an example of multilayer ceramicelectronic devices is produced by alternately stacking, for example,ceramic green sheets and internal electrode layers having apredetermined pattern, then making the same one body to obtain a greenchip and simultaneously firing the green chip.

The internal electrode layers of the multilayer ceramic capacitor asabove are made to be one body with ceramic dielectrics by firing, so ithas been necessary to select materials not reacting with ceramicdielectrics.

Conventionally, platinum, palladium and other precious metals have beenused as materials for composing internal electrode layers. However,since precious metals are expensive, it has been a cause of high costsof produced capacitors.

While, in recent years, it became possible to use nickel and otherinexpensive base metals as materials composing internal electrodes and awide reduction of the costs has realized.

Conventionally, a variety of proposals have made on dielectric ceramiccompositions wherein an inexpensive base metal can be used as a materialof internal electrodes. For example, in the Japanese Unexamined PatentPublication No. 6-45182, a dielectric ceramic composition wherein adielectric oxide (note that 0≦x≦0.25, 0≦y≦0.05, 0.1≦z≦0.3,1.000≦m≦1.020) indicated by a composition formula[(Ba_(1-x-y)Ca_(x)Sr_(y))O]_(m)(Ti_(1-z)Zr_(z))O₂ is a main component isdisclosed. In the Japanese Unexamined Patent Publication No. 6-342735, adielectric ceramic composition wherein BaTiO₃ is a main component isdisclosed. In the Japanese Unexamined Patent Publication No. 10-335169,a dielectric ceramic composition wherein a dielectric oxide (note that0≦x≦1.00, 0.9≦y≦1.00, 0.75≦m≦1.04) indicated by a composition formula(Sr_(1-x)Ca_(x))_(m)(Ti_(1-y)Zr_(y))O₃ is a main component is disclosed.

On the other hand, along with electronic devices getting more compact inrecent years, a more compact and larger capacity multilayer ceramiccapacitor has been demanded. To realize a more compact larger capacitymultilayer ceramic capacitor, it is necessary to make a thickness of onedielectric layer as thin as possible and to increase the number oflayers to be stacked in a predetermined size as much as possible(stacking more layers).

However, as dielectric layers get thinner and stacked more, a shape ofan obtained ceramic capacitor is liable to cause anisotropy. Whenanisotropy arises in a shape of a capacitor, tractability at the time ofmounting the capacitor on a substrate, etc. declines.

Also, as dielectric layers get thinner and stacked more, electriccharacteristics, such as static capacitance and insulation resistance,have been also liable to decline.

Furthermore, as dielectric layers get thinner and stacked more, cracks(particularly, inner cracks) have been liable to occur in an obtainedcapacitor. When a crack arises inside a capacitor, it cannot endure tobe used as a capacitor.

DISCLOSURE OF INVENTION

A first object of the present invention is to provide a method ofproducing a multilayer ceramic capacitor and other multilayer ceramicelectronic devices wherein structural defaults, such as shapeanisotropy, hardly arise, capable of improving electric characteristicsand suppressing deterioration thereof.

A second object of the present invention is to provide a method ofproducing a multilayer ceramic capacitor and other multilayer ceramicelectronic devices having dielectric layers of a certain composition bywhich an occurrence of cracks and other structural defaults aresuppressed even when the dielectric layers get thinner and stacked more.

To attain the first object, according to a first aspect (a firstinvention) of the present invention, there is provided a method ofproducing a multilayer ceramic electronic device, having a firing stepfor firing a pre-firing element body wherein a plurality of dielectriclayers and internal electrode layers containing a base metal arealternately arranged, characterized in that the firing step has atemperature raising step for raising a temperature to a firingtemperature; and hydrogen is continued to be introduced from a point intime of the temperature raising step.

To attain the second object, according to a second aspect (a secondinvention) of the present invention, there is provided a method ofproducing a multilayer ceramic electronic device including a firing stepfor firing a pre-firing element body, wherein a plurality of dielectriclayers containing a material indicated by a composition formula{(Sr_(1-x)Ca_(x))O}_(m)·(Ti_(1-y)Zr_(y))O₂, wherein m, x and yindicating respective mole ratios in the composition formula have arelationship of 0.75≦m<1.08, 0≦x≦1.00 and 0.5≦y≦1.00, and internalelectrode layers containing a base metal are alternately arranged,wherein the firing step includes a temperature raising step for raisinga temperature to a firing temperature; and hydrogen is continued to beintroduced from a point in time of the temperature raising step.

In both of the first and second inventions, it is sufficient to raisethe temperature to a firing temperature in the temperature raising stepand a process thereof is not particularly limited. For example, it maybe raised at a predetermined temperature raising rate to reach thefiring temperature, or after raising the temperature once to be apredetermined temperature (for example, lower than the firingtemperature) and lowering the temperature (for example, to the roomtemperature), introduction of the hydrogen may be performed as above toraise to the firing temperature for perform firing.

Note that both of the first and second inventions normally furtherinclude a step of removing a binder before the above firing step.

When raising the temperature to a predetermined temperature (forexample, lower than the firing temperature) and lowering from thepredetermined temperature (for example, to the room temperature), thenintroducing hydrogen to raise to the firing temperature so as to performfiring, the predetermined temperature is preferably 1000° C. or more inthe first invention and more than 800° C. in the second invention.

Both in the first and second inventions, a wet nitrogen gas ispreferably introduced as an atmosphere gas before introducing hydrogen.Accordingly, an atmosphere gas after introducing hydrogen is a mixed gasatmosphere of wet nitrogen and hydrogen.

In the first invention, the temperature of introducing hydrogen ispreferably 1000° C. or more in the first invention, while more than 800°C., more preferably 1050° C. or more in the second invention.

Both in the first and second inventions, the temperature of introducinghydrogen is preferably lower than the above firing temperature.

In the first invention, an atmosphere temperature may be raised at apredetermined raising rate after introducing hydrogen, or the atmospheretemperature may be raised at a predetermined rate after keeping it atthe atmosphere temperature at the time of introducing hydrogen for apredetermined time.

In the first invention, a method of introducing hydrogen is notparticularly limited and, for example, hydrogen of a predeterminedconcentration may be introduced from the beginning of the introductionor the hydrogen concentration to be introduced may be gradually changed.

In both of the first and second inventions, it is preferable thathydrogen is introduced so that a difference of oxygen partial pressuresbefore and after the hydrogen introduction becomes 6 digits or more atthe hydrogen introduction temperature.

In both of the first and second inventions, the above firing step mayfurther includes a temperature holding step for holding the firingtemperature and a temperature lowering step for lowering from the firingtemperature and hydrogen introduction may be stopped from a point intime of the temperature lowering step. When stopping the hydrogenintroduction from a point in time of the lowering step, a temperature atthe time of stopping the hydrogen introduction is preferably 1100° C. orless in the first invention, while 1200° in the second invention.

In both of the first and second inventions, the above pre-firing elementbody preferably has 50 or more dielectric layers.

In both of the first and second inventions, the base metal is preferablynickel or a nickel alloy.

In the first invention, the above dielectric layer preferably has a maincomponent containing BaTiO₃. In the first invention, it is alsopreferable that the above dielectric layer has a main componentcontaining (BaCa)(TiZr)O₃.

In both of the first and second inventions, it is preferable that theabove multilayer ceramic electronic device is a multilayer ceramiccapacitor.

OPERATION AND EFFECTS OF INVENTION

Conventionally, when producing a multilayer ceramic electronic device,such as a multilayer ceramic capacitor, an oxygen partial pressure wasaccurately controlled under a mixed gas atmosphere of wet nitrogen andhydrogen from an initial stage (around the room temperature) of atemperature raising step in a step of firing a pre-firing element body,such as a green chip, having dielectric layers and internal electrodelayers. Namely, by introducing hydrogen from the initial stage of thetemperature raising step, the oxygen partial pressure was kept low tostrengthen a reducing state, and thereby, oxidization of a base metal(for example, Ni, etc.) contained in the internal electrode wasprevented.

On the other hand, in the first invention, when firing the pre-firingelement body, hydrogen is continued to be introduced from a point intime of the temperature raising step for raising to the firingtemperature. On the hydrogen introduction, the oxygen partial pressureabruptly changes (preferably, 6 digits or more) and the reducing statebecomes stronger comparing with that before the hydrogen introduction.

In the temperature raising step before the hydrogen introduction, thebase metal contained in the internal electrode becomes oxidized. In thefirst invention, the temperature is raised without introducing hydrogenuntil the base metal contained in the internal electrode becomesoxidized, and then, hydrogen is introduced to reduce the oxidized basemetal. Therefore, improvement effects in a variety of characteristicscan be obtained according to the first invention. For example, effectsof increasing the dielectric constant (static capacitance), improvingdefaults of the insulation resistance (IR), and suppressing structuraldefaults, such as suppressing an expansion in the direction of stackedlayers which is noticeable when the number of layers is great, can bementioned.

Namely, according to the first invention, it is possible to provide amethod of producing a multilayer ceramic capacitor and other multilayerceramic electronic devices wherein structural defaults, such as shapeanisotropy, are hardly caused even when dielectric layers become thinnerand stacked more, moreover, electric characteristics are improved whilesuppressing deterioration thereof.

Also, in the conventional firing method explained above, since differentmaterials, that is, dielectrics and internal electrodes were fired at atime, a stress caused by a difference of contraction behaviors anddifference of contraction percentages was generated inside themultilayer ceramic electronic device. Due to the stress, cracks werecaused in the multilayer ceramic electronic devices in some cases.

On the other hand, it is characterized in the second invention that whenfiring a pre-firing element body having dielectric layers of a specificcomposition, hydrogen is continued to be introduced from a point in timeof the temperature raising step for raising to a firing temperature.

By introducing hydrogen from a point in time of the temperature raisingstep, sintering of internal electrodes and valid dielectric layerssandwiched by the internal electrodes is respectively accelerated from apoint in time of the temperature raising step. A ceramic dielectricsubjected to a sintering process as such gains more plasticity in thetemperature holding step for holding the firing temperature for apredetermined time, consequently, a stress inside the chip generatedduring the steps of the temperature raising to the temperature holdingcan be easily released. As a result, it is possible to produce amultilayer ceramic electronic device having dielectric layers of aspecific composition wherein an occurrence of structural defaults, suchas cracks, can be suppressed.

Namely, according to the second invention, it is possible to provide amethod of producing a multilayer ceramic capacitor and other multilayerceramic electronic devices having dielectric layers of a specificcomposition wherein structural defaults, such as cracks, are hardlycaused even if the dielectric layer becomes thinner and stacked more.

Note that in the Japanese Unexamined Patent Publication No. 5-283278, itis disclosed that by changing a water temperature of a wetter from apoint in time of a temperature raising step for raising to a firingtemperature under a mixed gas atmosphere of wet nitrogen and hydrogen atthe time of firing a pre-firing element body, an oxygen partial pressureunder the mixed gas atmosphere of wet nitrogen and hydrogen is lowered.The wetter indicates water for humidifying used for producing a mixedgas atmosphere of wet nitrogen and hydrogen.

In the technique described in the Publication, however, hydrogen isintroduced from the beginning of the temperature raising step in orderto prevent the base metal contained in internal electrodes from becomingoxidized, thus, a change of an oxygen partial pressure is very small,which is 3 digits or less even if the wetter temperature is changed.

Multilayer ceramic electronic devices to which the present invention canbe applied are not particularly limited and multilayer ceramiccapacitors, piezoelectric elements, chip varistors, chip thermisters,chip resistance and other surface-mounted device (SMD) chip typeelectronic devices can be mentioned.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitoraccording to an embodiment of the present invention; and

FIG. 2 is a graph of a relationship of a temperature at the time ofstarting hydrogen introduction and a crack occurrence rate.

BEST MODE FOR CARRYING OUT THE INVENTION

Below, the present invention will be explained based on an embodimentshown in the drawings.

First, a multilayer ceramic capacitor is explained as an example ofmultilayer ceramic electronic devices, and then, a production methodthereof will be explained.

As shown in FIG. 1, a multilayer ceramic capacitor 1 as a multilayerceramic electronic device comprises a capacitor element body 10 whereina plurality of dielectric layers 2 and internal electrode layers 3 arealternately arranged. At both end portions of the capacitor element body10 are formed a pair of external electrodes 4 respectively conductivewith the plurality of internal electrode layers 3 alternately arrangedinside the element body 10.

The internal electrode layers 3 are stacked so that the respective endsurfaces alternately expose to surfaces of facing two end portions ofthe capacitor element body 10. The pair of external electrodes 4 areformed at both end portions of the capacitor element body 10 andconnected to the exposed end surfaces of the alternately arrangedinternal electrode layers 3 to compose a capacitor circuit.

In the first invention, the dielectric layers 2 are not particularlylimited and, for example, composed of a dielectric ceramic compositionbelow.

In the first invention, the dielectric ceramic composition preferablyhas a main component containing, for example, calcium titanate,strontium titanate and/or barium titanate and has reducing resistingproperty. The main component preferably contains, for example, adielectric oxide indicated by a composition formula(Ba_((1-x))Ca_(x))_(A)(Ti_((1-z))Zr_(z))_(B)O₃. In this case, A, B, xand z are all in any range and, for example, 0.95<A/B<1.02, 0≦x≦1.00 and0≦z≦1.00.

In the first invention, the dielectric ceramic composition may include asubcomponent containing at least one kind selected from oxides of Sr, Y,Gd, Tb, Dy, V, Mo, Zn, Cd, Ti, Sn, W, Ba, Ca, Mn, Mg, Cr, Si and P otherthan the above main component.

As a composition example of the dielectric layer 2, for example, anembodiment below can be mentioned.

First, as a main component, for example, a dielectric oxide having acomposition indicated by [(Ba_(1-x)Ca_(x))O]_(m)(Ti_(1-z)Zr_(z))O₂ isused. In this case, x, z and m are preferably 0≦x≦0.25, 0≦z≦0.3 and1.000≦m≦1.020. In a main component as such, at least one kind selectedfrom oxides of Mn, Y, V, Si and Mg and/or compounds which become oxidesby firing is preferably included. More preferably, 0.01 to 0.5 wt % ofan oxide of Mn and/or a compound which becomes an oxide by firing in aconversion of an oxide (MnO), 0.05 to 0.5 wt % of an oxide of Y and/or acompound which becomes an oxide by firing in a conversion of an oxide(Y₂O₃) and 0.005 to 0.3 wt % of an oxide of V and/or a compound whichbecomes an oxide by firing in a conversion of an oxide (V₂O₅) arepreferably contained. Still more preferably, not more than 0.25 wt % ofSiO₂ is further contained. Note that not more than about 0.5 wt % of aMg oxide may be contained other than the above composition.

Secondary, as a main component, for example, BaTiO₃ is used. An atomicratio (Ba/Ti ratio m) of Ba and Ti in this case is preferably0.95<m<1.01. At least one kind selected from oxides of Y, Si, Mg, Mn, Crand V and/or compounds which become oxides by firing is preferablycontained in a main composition as such. More preferably, with respectto 100 moles of BaTiO₃, 0.2 to 5 moles of Y₂O₃, 0.2 to 5 moles of SiO₂and 0 to 3 moles of MgO are contained. Still more preferably, 0.2 to 5moles of MnO or Cr₂O₃ is contained. Furthermore, it is preferable tocontain not more than 0.2 mole of V₂O₅ is contained. Note that at leastone kind of elements of Dy, Ho, Gd, Mo, Sr and Yb may be contained otherthan the above composition.

Note that in the first invention, the composition of the dielectriclayers 2 is not limited to the above.

In the second invention, the dielectric layer 2 includes a dielectricceramic composition below.

In the second invention, the dielectric ceramic composition has a maincomponent containing a dielectric oxide indicated by a compositionformula {(Sr_(1-x)Ca_(x))O}_(m)·(Ti_(1-y)Zr_(y))O₂. At this time, anoxygen (O) amount may be slightly different from a stoichiometriccomposition of the above formula.

In the above composition formula, x is 0≦x≦1.00. The x indicates thenumber of Ca atoms and by changing the x, that is, a Ca/Sr ratio, acapacity temperature coefficient and a specific dielectric constant canbe freely controlled. Note that in the second invention, the ratio of Srand Ca may be any and only one of the two may be contained.

In the above composition, y is 0.5≦y≦1.00, preferably 0.93≦y≦1.00. Bymaking the y 0.5 or more, dependency on a frequency by a staticcapacitance and dielectric loss becomes small. The y indicates thenumber of Zr atoms, and reducing resistance tends to increase byreplacing ZrO₂ which is hard to be reduced comparing with TiO₂.

In the above composition, the molar ratio m is 0.75≦m<1.08, preferably0.75≦m≦1.04 and still more preferably 0.970≦m≦1.030. By making the m0.75 or more, dependency on a frequency by a static capacitance anddielectric loss becomes small. By making the m less than 1.08, a finesintered body can be obtained without heightening a firing temperature.

In the second invention, the dielectric ceramic composition may be addeda predetermined amount of first subcomponent containing at least oneselected from oxides of V, Nb, W, Ta and Mo and/or compounds whichbecome oxides of them after firing. By adding a predetermined amount ofsuch first subcomponent, firing at a low temperature becomes possiblewithout deteriorating dielectric characteristics and an accelerationlifetime (high temperature load lifetime) of an insulation resistancecan be improved even when the dielectric layers are made thinner. Whenadding the first subcomponent, a ratio of the first subcomponent withrespect to 100 moles of the above main component is 0.01 mole≦firstsubcomponent≦2 moles, preferably 0.02 mole≦first subcomponent≦1.5 moles.

In the second invention, the dielectric ceramic composition may be addeda predetermined amount of a second subcomponent containing an oxide ofMn (for example, MnO) and/or a compound (for example, MnCO₃) whichbecomes an oxide of Mn by firing. The second subcomponent has effects ofaccelerating sintering and giving reducing resistance. When adding thesecond subcomponent, the ratio of the second subcomponent with respectto 100 moles of the main component is 0 mole≦second subcomponent<10moles, preferably 0.05 mole≦second subcomponent≦5 moles.

In the second invention, the dielectric ceramic composition may be addeda predetermined amount of a third subcomponent containing at least oneselected from SiO₂, MO (note that M is at least one element selectedfrom Ba, Ca, Sr and Mg), Li₂O and B₂O₃. The third subcomponent servesmainly as a sintering auxiliary agent. When adding the thirdsubcomponent, the ratio of the third subcomponent with respect to 100moles of the above main component is 0 mole<third subcomponent<15 moles,preferably 0.2 mole≦third subcomponent≦6 moles in a conversion of oxide.

In the second invention, a dielectric ceramic composition may be added apredetermined amount of fourth subcomponent containing oxides of R (notethat R is at least one kind selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu). The fourth subcomponent has aneffect of reducing dependency on a frequency by a static capacitance anddielectric loss. In the case of adding the fourth subcomponent, theratio of the fourth subcomponent with respect to 100 moles of the abovemain component is 0.02 mole≦fourth subcomponent<2 moles, preferably 0.02mole≦fourth subcomponent≦0.6 mole.

The number of layers to be stacked, a thickness and other conditions ofthe respective dielectric layers 2 may be suitably determined inaccordance with an object and use. The thickness of the respectivedielectric layers 2 is 30 μm or less in the present embodiment,preferably 10 μm, more preferably 5 μm, still more preferably 3 μm andits lower limit is preferably 0.2 μm or so. The number of stacked layersin the dielectric layers 2 is preferably 50 or more, more preferably 100or more and still more preferably 300 or more. Furthermore, thedielectric layer 2 is composed of grains and a grain boundary phase, andan average particle diameter of the grains of the dielectric layer 2 ispreferably 0.1 to 5 μm or so. Normally, the grain boundary phase has asits components oxides of materials composing the dielectric material orthe internal electrode material, oxides of separately added materials,furthermore, oxides of materials mixed in as impurities during thesteps, and is composed of glass or vitreous material.

Conductive materials contained in the internal electrode layer 3 is notparticularly limited and a base metal can be used when components of thedielectric layer 2 have reducing resisting property. As the base metal,nickel or a nickel alloy is preferable. A content of nickel in the alloyis preferably 90 wt % or more. Note that the nickel or nickel alloy maycontain about 0.1 wt % or less of a variety of trace components, such asphosphorous, iron and magnesium. A thickness of the internal electrodelayer 3 may be suitably determined in accordance with use, etc. andnormally 0.5 to 5 μm and preferably 0.5 to 2 μm or so.

Materials of the external electrodes 4 are not particularly limited andnormally copper, a copper alloy, nickel, a nickel alloy, etc. are used,but silver, an alloy of silver and palladium etc. can be also used.Also, a thickness of the external electrodes 4 is not limited andnormally 10 to 50 μm or so.

A shape and size of the multilayer ceramic capacitor 1 may be suitablydetermined in accordance with an object and use, and the size isnormally 0.6 to 5.7 mm in the lengthwise×0.3 to 5.0 mm in thecrosswise×0.1 to 3.0 mm in height or so when the capacitor 1 isrectangular parallelpiped.

Particularly, when the multilayer ceramic capacitor 1 is produced byusing a later explained firing method in the first invention, the shapedoes not cause any anisotropy. Specifically, assuming the maximumthickness of the multilayer ceramic capacitor 1 is b (refer to FIG. 1)and the minimum thickness is a (refer to FIG. 1) and a rate ofdifference of the thickness is calculated by a formula ({(b−a)/a}×100),the value can be made smaller than that in the conventional capacitorsand preferably the value can be made nearly 0%. A degree of anisotropyoccurrence is changed in accordance with a composition and designs, suchas the number of stacked layers and thickness, of the dielectric layers2, and a value of the formula ({(b−a)/a}×100) can be made 6% or lesswhen a size of the capacitor element body 10 is, for example, 3.2 mm inlengthwise×1.6 mm in crosswise×0.6 mm in thickness, the number of layersof the dielectric layers 2 is 100, a thickness of the dielectric layers2 is 4 μm and a thickness of the internal electrode layers 3 is 2 μm.

Note that in the conventional multilayer ceramic capacitor, 8% or so wasthe limit by the same size and the same composition system.

Also particularly, when the multilayer ceramic capacitor 1 is producedby using a later explained firing method in the second invention, anoccurrence of cracks can be suppressed. Specifically, for example, in amultilayer ceramic capacitor having 330 dielectric layers and a size of4.5 mm in lengthwise×3.2 mm in crosswise×2.3 mm in height or so, thecrack occurrence rate can be suppressed to 90% or less, preferably 60%or less and more preferably 5% or less. Note that when producing amultilayer ceramic capacitor of the same size having 330 dielectriclayers by using the conventional firing method, the crack occurrencerate was 100%.

The multilayer ceramic capacitor 1 according to the present embodimentcan be produced by preparing a green chip by a normal printing method orsheet method using a paste, firing the same, then, printing ortransferring an external electrode and firing.

An example of a production method of the multilayer ceramic capacitor 1according to the present embodiment will be explained.

First, a dielectric layer paste, an internal electrode layer paste andan external electrode layer paste are prepared.

The dielectric layer paste is for forming the dielectric layers 2 (referto FIG. 1) and composed of an organic solvent based paint or awater-soluble solvent based paint obtained by kneading dielectricmaterials and a binding agent.

As the dielectric materials, composite oxides and a variety of compoundswhich become oxides, for example, suitably selected from carbonate,nitrate, hydroxides, organic metal compounds, etc. can be mixed to use.A content of the dielectric material in the dielectric layer paste maybe 15 to 50 wt % or so.

As the binding agent, which is not particularly limited, a variety ofbinders, such as a cellulosic resin, butyral system resin, acrylicresin, olefinic system resin urethane system resin and styrene systemresin, can be used. A content of the binding agent in the dielectriclayer paste is not particularly limited and may be 1 to 15 wt % or so.

Additives selected from a variety of dispersants, plasticizers, etc. maybe included in accordance with need in the dielectric layer paste.

The internal electrode layer paste is for forming the internal electrodelayers 3 (refer to FIG. 1) and prepared by kneading the above conductivematerial, etc. with the above binding agent. A content of the bindingagent in the internal electrode paste is not particularly limited andmay be a normal content of, for example, 1 to 15 wt % or so. A contentof the conductive material in the internal electrode paste may be 40 to60 wt %. Additives selected from a variety of dispersants, plasticizers,dielectrics, insulating materials, etc. may be included in accordancewith need in the internal electrode paste.

The external electrode paste is prepared in the same way as the internalelectrode paste.

When using a printing method, the dielectric layer paste and theinternal electrode paste of a predetermined pattern are printed bystacking on a substrate of polyethylene terephthalate, etc., cut to be apredetermined shape, then, removed from the substrate so as to obtain agreen chip. While, when using a sheet method, a green sheet is formed byusing the dielectric layer paste, printing the internal electrode pasteby a predetermined pattern thereon, then, stacking so as to obtain agreen chip. Note that a thickness of the formed dielectric green sheetis suitably determined in accordance with the thickness of thedielectric layer 2 explained above. A thickness of the internalelectrode pattern is suitably determined in accordance with thethickness of the internal electrode layer 3 explained above.

Next, the obtained green chip is subjected to binder removing and firingprocessing.

An atmosphere at the time of the binder removing processing of the greenchip is not particularly limited and the processing can be performed ina variety of atmospheres, for example, in the air, in a wet nitrogen gasatmosphere, or a mixed gas of wet nitrogen and hydrogen, etc. If thebinder removing processing is insufficient before firing, cracks andother structural defaults easily arise during main firing due toresidual carbon. Thus, it is necessary that the binder removingprocessing is sufficiently performed prior to the firing. Note that anobject of the binder removing processing is absolutely to remove abinder from the green chip and not to sinter the dielectric. Therefore,normally the binder is sufficiently removed when the temperature is notraised to an extent that the dielectric starts to be sintered,specifically, for example, at less than 1000° C., preferably 800° c. orless in the first invention and, for example, 800° C. or less in thesecond invention. The binder removing is normally performed by keepingat a predetermined temperature for about 0.5 to 24 hours. It ispreferable because by doing so, the binder is sufficiently removed. Inthe second invention, the temperature may be once cooled to the roomtemperature, etc. after the binder removing so as to proceed to a firingstep, or the firing step may be successively taken after the binderremoving. Those characterized in the first and second inventions are allbelong to the firing step after the binder removing processing.

Then, the green chip after the binder removing step is subjected to thefiring step.

In the present embodiment, the firing step includes a temperatureraising step, a temperature holding step and a temperature loweringstep.

The temperature raising step is a step for raising an atmospheretemperature to a firing temperature. The temperature raising step isjust required to raise the temperature to the firing temperature and theprocess is not particularly limited. To obtain the effects of the firstinvention, the temperature may be raised to the firing temperature at apredetermined raising rate, or the temperature may be once raised to apredetermined temperature (for example, lower than the firingtemperature) and lowered from the predetermined temperature (forexample, to the room temperature), then, raised to the firingtemperature at a predetermined raising rate. The predeterminedtemperature in this case is preferably 1000° C. or more, more preferably1150° C. or so in the first invention and preferably more than 800° C.,more preferably more than 1050° C. in the second invention.

In the initial stage of the temperature raising step, the temperature israised under an atmosphere gas using a wet nitrogen gas. In the firstinvention, the atmosphere makes base metals included in internalelectrodes be easily oxidized. In the second invention, it is consideredthat sintering of dielectrics between internal electrodes and electrodesis accelerated, furthermore, plasticity of the dielectrics in thetemperature holding step is increased.

Then, hydrogen is continued to be introduced from a point in time of thetemperature raising step. In the first invention, the hydrogenintroduction method is not particularly limited and, for example, thehydrogen of a predetermined concentration may be introduced from thebeginning of the introduction, or the hydrogen may be introduced byusing concentration gradient toward the predetermined concentration,such that the hydrogen concentration becomes 5 percent by volume or soat the time that a temperature of the atmosphere is raised to about 100°C. In any cases, an oxygen partial pressure in the firing atmospheredeclines and the reducing state becomes strong.

In the second invention, hydrogen is continued to be introduced from apoint in time of the temperature raising step and abruptly reduces theoxygen partial pressure in the firing atmosphere to make the reducingstate strong at a time. As a result, oxidization of the internalelectrodes is prevented. When firing is carried out by in this method,the stress caused by a difference of contraction behavior between theinternal electrodes and the dielectrics generated from the temperatureraising step to the temperature holding step can be released by plasticstrain of the dielectrics. Therefore, it is considered that anoccurrence of cracks is suppressed.

Note that since the oxygen partial pressure widely changes in accordancewith a temperature, hydrogen concentration and a temperature of awetter, it is important to carefully control them. For example, in thecase of introducing no hydrogen (0%) and the case of introducinghydrogen by 5% at 50° C., the oxygen partial pressures are about 1×10⁻²¹Pa and about 4×10⁻⁷⁰ Pa, respectively, that is, the difference becomesnearly 50 digits. Also at 500° C., in the case of introducing 0% ofhydrogen and the case of 5% of hydrogen, the oxygen partial pressuresare about 3×10⁻⁶ Pa and about 6×10⁻²⁴ Pa, that is, the differencebecomes more than 10 digits. Furthermore, at 1100° C. also, in the caseof introducing 0% of hydrogen and the case of 5% of hydrogen, the oxygenpartial pressures are about 2×10⁻¹ Pa and about 2×10⁻⁹ Pa, that is, thedifference becomes 8 digits.

In the firing methods of the first and second inventions, it ischaracterized that preferably the oxygen partial pressure is abruptlychanged by at least 6 digits in a specified temperature range. Namely,it is preferable to introduce hydrogen so that a difference of oxygenpartial pressures before and after the hydrogen introduction becomes 6digits or more at the temperature of the hydrogen introduction.

Note that the oxygen partial pressure can be also changed by changingthe temperature of the wetter. However, in this method, it is difficultto change the oxygen partial pressure by 6 digits or more particularlyat a high temperature of 1000° C. or more and the effects in the firstand second inventions cannot be obtained.

Note that the atmosphere after the hydrogen introduction preferablyincludes nitrogen as a main component and is wetted by a vapor pressureof 1 to 10 percent by volume of hydrogen and 0 to 50° C. in the firstinvention. While in the second invention, it is preferable to includenitrogen as a main component and is wetted by a vapor pressure of 0.1 to10 percent by volume of hydrogen and 0 to 70° C. For example, a wetter,etc. can be used for wetting. The wetter temperature may be the same ordifferent before and after the beginning of the hydrogen introduction.

In the first invention, it is characterized that Ni is intentionallyoxidized. Generally, deterioration of characteristics and occurrence ofstructural defaults are liable to be caused due to oxidization of Niduring firing, so firing is carried out while suppressing oxidization ofNi. However, in the first invention, sintering of Ni can be made slow byoxidizing Ni to a certain extent. After that, the oxidized base metalcan be abruptly reduced by introducing hydrogen. As a result, the basemetal (for example, Ni) contained in the internal electrodes can beprevented from becoming spheroidized, expansion in a direction ofstacked layers, which is noticeable when stacking a great number oflayers, can be effectively suppressed and a multilayer ceramic capacitor1 having less structural defaults can be produced. Moreover, thedielectric constant (static capacitance) of the obtained multilayerceramic capacitor 1 is increased and inferiority of insulationresistance (IR) can be improved.

In the second invention, the initial stage of the temperature raisingstep is carried out under an atmosphere gas using a wet nitrogen gas andsintering of the internal electrodes and the dielectrics is accelerated,so plasticity of the dielectrics is increased. After that, hydrogen isintroduced and oxidization of base metal internal electrodes isprevented. As a result, a multilayer ceramic capacitor 1 havingdielectric layers of a specific composition wherein an occurrence ofcracks and other structural defaults are suppressed can be produced.

In the first invention, in the case of raising the temperature to thefiring temperature at a predetermined raising rate, the temperature ofhydrogen introduction is not particularly limited, but it is preferably1000° C. or more, more preferably 1100° C. or more, and still morepreferably 1150° C. or more. By setting the lower limit of thetemperature of the hydrogen introduction at 1000° C., an improvement ina defective fraction of insulation resistance (IR) of the obtainedcapacitor 1 can be expected. There is a tendency that the more thenumber of stacked layers, the more noticeable deterioration ofinsulation resistance, however, by starting hydrogen introduction at1000° C. or more, deterioration of the insulation resistance isprevented even in a multilayer product having 300 layers or more.Namely, by setting the temperature at the time of starting the hydrogenintroduction at 1000° C., effects particularly in the case where a greatnumber of layers are stacked can become remarkable.

Note that in the first invention, in the case where the temperature isnot raised to the firing temperature at a predetermined raising rate butonce raised to a predetermined temperature (for example, 1150° C. orso), which is lower than the firing temperature, lowered from thepredetermined temperature to, for example, the room temperature, andthen, hydrogen is introduced, the temperature of the hydrogenintroduction is not particularly limited, so the hydrogen introductionmay be performed before a base metal included in the internal electrodesis oxidized. The temperature may be, for example, the room temperature(25° C. or so). In the same way, the temperature at the time ofintroducing hydrogen after once raising and lowering the temperature topredetermined temperatures may be the room temperature. The reasonthereof is not exactly clear, but it is deemed that it is becauseoxidization of internal electrodes progresses and sintering ofdielectric layers progresses by raising the temperature to thepredetermined temperature without introducing any hydrogen.

In the first invention, it is also preferable to hold the temperature ofhydrogen introduction, for example, for 0 to 180 minutes or so,preferably 0 to 120 minutes or so.

On the other hand, in the first invention, when introducing hydrogenafter reaching to the firing temperature (a sintering temperature of thedielectrics) or introducing hydrogen for the first time from a point intime of the temperature lowering step, sintering of the dielectriclayers becomes insufficient, which may lead to deterioration ofcharacteristics. Therefore, the upper limit of the temperature at thetime of starting the hydrogen introduction is preferably the firingtemperature (at the time when the temperature reached the firingtemperature through the temperature raising step and before enteringinto the temperature holding step).

In the second invention the temperature of hydrogen introduction ispreferably over 800° C., more preferably over 1050° C., and still morepreferably over 1200° C. By setting the lower limit of the temperatureof the hydrogen introduction at more than 800° C., a reduction ofinternal cracks and other structural defaults of the capacitor 1 can beexpected. The occurrence of internal cracks tends to increase as thenumber of stacked layer increases, however, the occurrence of internalcracks is suppressed even in a product wherein a great number of layersare stacked by starting the hydrogen introduction at over 800° C.Namely, by setting the temperature of starting the hydrogen introductionat over 800° C., the effects can become more remarkable when the numberof dielectric layers is great.

On the other hand, in the second invention, when hydrogen is introducedafter entering into the temperature holding step, breaks often occur inthe internal electrodes and internal electrode components are dispersedin the dielectric layers, which may lead to deterioration ofcharacteristics. Accordingly, the upper limit of the temperature ofstarting the hydrogen introduction is preferably the firing temperature(at the time the temperature reached the firing temperature in thetemperature raising step and before entering into the temperatureholding step).

Both in the first and second inventions, the temperature raising rate ispreferably 50 to 500° C./hour, more preferably 200 to 300° C./hour. Inthe second invention, when the temperature raising rate is too slow, ittakes too much time for firing and the productivity may decline. Whilewhen the temperature raising rate is too fast, delamination and otherdefaults may occur.

The temperature holding step is for holding the temperature at the abovefiring temperature. In the temperature holding step, it is preferablethat the above atmosphere is not changed and that the firing temperatureis kept for a certain time under a mixed gas atmosphere of wet nitrogengas and hydrogen gas.

The firing temperature is normally a sintering temperature of thedielectrics and preferably 1000 to 1400° C., more preferably 1150 to1350° C. in the first invention and 1200 to 1380° C. in the secondinvention. Both in the first and second inventions, when the firingtemperature is too low, a sintered body cannot be made sufficientlyfine. While when the firing temperature is too high, in the firstinvention, capacity-temperature characteristics of the obtainedmultilayer ceramic capacitor 1 is declined as a result of breaks ofelectrodes or dispersion of materials composing the internal electrodescaused by abnormal sintering of the internal electrodes. In the secondinvention, electric characteristics of the obtained multilayer ceramiccapacitor 1 deteriorates as a result of breaks of electrodes ordispersion of materials composing the internal electrodes caused byabnormal sintering of the internal electrodes.

A holding time of the firing temperature is preferably 0.5 to 8 hours,more preferably 1 to 3 hours in the first invention and 0.5 to 16 hours,more preferably 1 to 12 hours in the second invention.

The temperature lowering step is a step for lowering the temperaturefrom the above firing temperature. In the temperature lowering step, thetemperature may be lowered in the mixed gas atmosphere of a wet nitrogengas and hydrogen gas without changing the atmosphere in the abovetemperature holding step, or the atmosphere may be changed from a pointin time of the temperature lowering step. When changing the atmosphere,it is changed to an atmosphere gas using a wet nitrogen gas by stoppingfrom a point in time of the temperature lowering step the hydrogencontinued to be introduced from a point in time of the above temperatureraising step. Namely, the temperature may be lowered under a mixed gasatmosphere of wet nitrogen and hydrogen until a point in time of thetemperature lowering step, and then in the wet nitrogen gas atmosphereby stopping the hydrogen introduction from a point in time of thetemperature lowering step. By doing so, the oxygen partial pressure isincreased to heighten an oxidizing state, consequently, annealingeffects of the dielectric layers can be obtained.

When stopping the hydrogen introduction, the temperature is preferably1100° C. or less, more preferably 1050° C. or less in the firstinvention. By setting the upper limit of the temperature of stopping thehydrogen introduction, annealing effects can be effectively obtained.Also, it is preferably 1200° C. or less, more preferably 1000° C. orless in the second invention. By setting the upper limit of thetemperature of stopping the hydrogen introduction, oxidization of theinternal electrodes and dispersion of internal electrode components intothe dielectric layers can be prevented.

The temperature lowering rate is preferably 50 to 500° C./hour, morepreferably 200 to 300° C./hour. When the temperature lowering rate istoo slow, productivity is liable to decline, while when the temperaturelowering rate is too fast, cracks may occur due to a heat-shock, etc.

It is preferable that annealing (heat treatment) is performed on a chipsintered body after the firing step, but it is not always necessary.Note that when the annealing effects are obtained in the abovetemperature lowering step, annealing thereafter becomes unnecessary. Theannealing is processing for re-oxidizing the dielectric layers, andthereby, insulation resistance of the capacitor 1 can be increased.

An oxygen partial pressure of the annealing atmosphere is preferably10⁻⁴ Pa or more, more preferably 10⁻¹ to 10 Pa. When the oxygen partialpressure is too low, the dielectric layers 2 are hard to be re-oxidized,while when the oxygen partial pressure is too high, the internalelectrode layers 3 are liable to be oxidized.

A holding temperature at the time of annealing is preferably 1100° C. orless, more preferably 500 to 1100° C. in the first invention, and 1200°C. or less, more preferably 500 to 1100° C. in the second invention.When the holding temperature is too low, re-oxidization of thedielectric layers becomes insufficient, insulation resistance declinesand its accelerated lifetime is liable to be short. While, when theholding temperature is too high, not only the internal electrodes areoxidized and the capacity declines, but reaction with a dielectric basearises and capacity-temperature characteristics, insulation resistanceand its accelerated lifetime are liable to be deteriorated. Note thatannealing can be composed only of a temperature raising step and atemperature lowering step. In this case, the temperature holding time iszero, and the holding time and the highest temperature are synonymous.

Annealing conditions other than the above are preferably the temperatureholding time is set to be 0 to 20 hours, more preferably 1 to 10 hours,a cooling rate is set to be 50 to 500° C./hour, more preferably 100 to300° C., and, for example, a wet nitrogen gas is introduced as anatmosphere gas of the annealing.

Note that in the same way as in the above firing, to wet a nitrogen gasor a mixed gas in the above binder removing and annealing processing,for example, a wetter, etc. can be used and a water temperature at thistime is preferably 5 to 75° C.

The binder removing processing, firing and annealing may be successivelyperformed or separately performed.

An obtained capacitor sintered body is subjected to end surfacepolishing, for example, by barrel polishing or sandblast, printed ortransferred an external electrode paste and fired to form the externalelectrodes 6 and 8. Firing conditions of the external electrode pasteare preferably, for example, at 600 to 800° C. for 10 minutes to 1 houror so using a mixed gas of a wet nitrogen gas and hydrogen gas. Onsurfaces of a pair of external electrodes 4 may be formed a coatinglayer (pad layer) by soldering, etc. in accordance with need.

The thus obtained multilayer ceramic capacitor 1 is mounted on a printedcircuit board by soldering, etc. and used in a variety of electronicequipments.

According to the first invention, expansion in the stacked layerdirection, which is noticeable when the number of stacked layers isgreat, can be suppressed and a multilayer ceramic capacitor 1 havingless structural defaults can be produced. Moreover, according to thefirst invention, the dielectric constant (static capacitance) of theobtained multilayer ceramic capacitor 1 increases and inferiority ofinsulation resistance (IR) improves.

According to the second invention, expansion in the stacked layerdirection, which is noticeable when the number of stacked layers isgreat, can be suppressed and a multilayer ceramic capacitor 1 havingdielectric layers of a specific composition, by which internal cracksand other structural defaults are less, can be produced.

Embodiments of the present invention were explained above, but thepresent invention is not limited to the embodiments and can be embodiedin a variety of ways within the scope of the present invention.

For example, in the above embodiments, a multilayer ceramic capacitorwas taken as an example of a multilayer ceramic electronic deviceaccording to the present invention, but the multilayer ceramicelectronic device according to the present invention is not limited to amultilayer ceramic capacitor and may be any devices having a body madeby alternately stacking dielectric layers and internal layers.

Next, examples wherein the embodiment of the present invention isdescribed more specifically will be used for explaining the presentinvention further in detail. Note that the present invention is notlimited to the embodiments.

EXAMPLE 1

First, a dielectric layer paste was prepared as described below.

As starting materials, powders of BaCO₃, CaCO₃, TiO₂, ZrO₂, MnCO₃, SiO₂,Y₂O₃, etc. having a particle diameter of 0.1 to 1 μm were used.

These powders were mixed to be a composition of 100 mole % by acomposition formula {(Ba_(0.95)Ca_(0.05)) (Ti_(0.8)Zr_(0.2))O₃} asmaterials wherein a part of BaTiO₃ is replaced by Ca and Zr by firing,0.2 mole % in a conversion of MnO, 0.16 mole % in a conversion of SiO₂and 0.3 mole % in a conversion of Y₂O₃, subjected to wet mixing using aball mill for 16 hours and dried to obtain a dielectric material.

A paste was obtained by mixing by using a ball mill 100 parts by weightof the obtained dielectric material, 4.8 parts by weight of acrylicresin, 40 parts by weight of methylene chloride, 20 parts by weight oftrichloroethane, 6 parts by weight of mineral spirits and 4 parts byweight of acetone.

Next, an internal electrode paste was prepared as described below. Apaste was obtained by kneading by using a triple-roll 100 parts byweight of Ni particle having an average particle diameter of 0.8 μm, 40parts by weight of organic vehicle (8 parts by weight of an ethylcellulose resin is dissolved in 92 parts by weight of butyl carbitol)and 10 parts by weight of butyl carbitol.

Next, an external electrode paste was prepared as described below. Apaste was obtained by kneading 100 parts by weight of Cu particle havingan average particle diameter of 0.5 μm, 35 parts by weight of organicvehicle (8 parts by weight of an ethyl cellulose resin is dissolved in92 parts by weight of butyl carbitol) and 7 parts by weight of butylcarbitol.

Next, the above dielectric layer paste was used for forming a greensheet of a thickness of 6 μm on a PET film, the internal electrode pastewas printed by a predetermined pattern thereon, and then, the greensheet was removed from the PET film.

Next, the green sheets and protective green sheets (on which theinternal electrode paste is not printed) were stacked and pressured toobtain a green chip. The number of stacked layers in the sheet havingthe internal electrodes were 100.

Then, the green chip is cut to a predetermined size and subjected to abinder removing step, firing step and annealing (heat treatment) toobtain a multilayer ceramic sintered body.

The binder removing processing was performed under conditions below.

-   -   temperature raising time: 15° C./hour    -   holding temperature: 280° C.    -   holding time: 8 hours    -   atmosphere: in the air

Firing was performed under conditions below.

First, the temperature was raised from the room temperature (25° C.) to1100° C. at a temperature raising rate of 200° C./hour under anatmosphere gas using a wet nitrogen gas (an oxygen partial pressure was10⁻¹ Pa or so). Then, hydrogen introduction was started at 1100° C. tochange to a mixed gas atmosphere of a wet nitrogen gas and hydrogen gas(5 percent by volume of H₂, and the oxygen partial pressure was 10⁻⁸ Paor so). The temperature was raised to the firing temperature of 1220° C.under the atmosphere.

Next, firing was performed by holding the firing temperature of 1220° C.for 2 hours without changing the atmosphere.

Then, the temperature was lowered to the room temperature (25° C.) at atemperature lowering rate of 200° C./hour without changing theatmosphere.

Annealing was performed under conditions below.

-   -   holding temperature: 1000° C.    -   holding time: 3 hours    -   temperature lowering rate: 300° C./hour    -   atmosphere: wet nitrogen gas    -   (oxygen partial pressure was 10⁻¹ Pa)

Note that to wet the atmosphere gas at the time of firing and annealing,a wetter with a water temperature of 20° C. was used.

Next, after polishing end surfaces of the multilayer ceramic sinteredbody by sandblast, the external electrode paste was transferred to theend surfaces, and external electrodes were formed by firing at 800° C.for 10 minutes under a mixed gas atmosphere of a wet nitrogen gas andhydrogen gas to obtain multilayer ceramic capacitor samples having acomposition shown in FIG. 1.

The obtained capacitor samples had a size of 3.2 mm×1.6 mm×0.6 mm,wherein the number of dielectric layers sandwiched by two internalelectrodes was 100, a thickness thereof was 3 μm and the thickness ofthe internal electrode layers was 1.5 μm.

Static capacitance, a defective fraction of insulation resistance (IR)and shape anisotropy of the obtained capacitor samples were evaluated,respectively.

The static capacitance (μF) was obtained by measuring static capacitanceof 10 capacitor samples at a reference temperature of 25° C. by adigital LCR meter (4274A made by YHP Company) under conditions of afrequency of 120 Hz and an input signal level (measurement voltage) of0.5 Vrms and calculating an average value thereof. The result was 13 μF.

The defective fraction (%) of insulation resistance (IR) was obtained byusing 100 capacitor samples. Those fell into IR<1×10⁸ Ù were judged tobe defective and a ratio of the defective in all quantity was obtainedby a percentage to be used as the defective fraction. The result was50%. Note that the insulation resistance (IR) was measured by using aninsulation resistance tester (R8340A made by Advantest Corporation)after applying a DC of 10V to the capacitor samples for 60 seconds at25° C.

The shape anisotropy was obtained by respectively measuring a maximumthickness (b) and a minimum thickness (a) of 20 capacitor samples,calculating by a formula {(b−a)/a}×100 a ratio (%) that a thicknessdifference differs and obtaining an average thereof. When the value wasless than 6%, “∘” was given, while “x” was given when 6% or more. As aresult, the present example was given “∘” and no shape anisotropy wasobserved.

EXAMPLE 2

Capacitor samples were obtained in the same way as in the Example 1except that hydrogen introduction was started at the time thetemperature was raised to 1150° C. in the firing step. Evaluation wasmade in the same way as in the Example 1.

As a result, the static capacitance of the obtained capacitor sampleswas 15 μF and the capacity was confirmed to be increased comparing withthe Example 1. The defective fraction of insulation resistance (IR) ofthe capacitor samples was 0% and the IR defective fraction was confirmedto be drastically improved comparing with the Example 1. The shapeanisotropy of the capacitor samples was “∘” and no shape anisotropy wasobserved.

EXAMPLE 3

Capacitor samples were obtained in the same way as in the Example 1except that hydrogen introduction was started at the time thetemperature was raised to 1220° C. in the firing step. Evaluation wasmade in the same way as in the Example 1.

As a result, the static capacitance of the obtained capacitor sampleswas 14 μF and the capacity was increased comparing with the Example 1.While, when comparing with the Example 2, a little decrease in thecapacity was confirmed. The reason is not exactly clear, but it isdeemed that it is because when hydrogen introduction starts at the timeof reaching the firing temperature, sintering of the dielectrics tendsto be insufficient, and thereby, the capacity decreases. The defectivefraction of insulation resistance (IR) of the capacitor samples was 0%and the IR defective fraction was confirmed to be drastically improvedcomparing with the Example 1. The shape anisotropy of the capacitorsamples was “∘” and no shape anisotropy was observed.

COMPARATIVE EXAMPLE 1

Capacitor samples were obtained in the same way as in the Example 1except that hydrogen introduction was started from the beginning oftemperature raising at the room temperature (25° C.) and the atmospherewas a mixed gas of a wet nitrogen and hydrogen in the firing step.Evaluation was made in the same way as in the Example 1.

As a result, the static capacitance of the obtained capacitor sampleswas 11 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 95%. The shape anisotropy of the capacitor sampleswas “x”. The respective evaluations were inferior to those of theExamples 1 to 3, and superiority of the Examples 1 to 3 was confirmed.

COMPARATIVE EXAMPLE 2

Capacitor samples were obtained in the same way as in the Example 1except that hydrogen introduction was started at the time thetemperature was raised to 800° C. in the firing step. Evaluation wasmade in the same way as in the Example 1.

As a result, the static capacitance of the obtained capacitor sampleswas 11 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 95%. The shape anisotropy of the capacitor sampleswas “x”. The respective evaluations were inferior to those of theExamples 1 to 3, and superiority of the Examples 1 to 3 was confirmed.

EXAMPLE 4

Capacitor samples were obtained in the same way as in the Example 1except that the number of dielectric layers sandwiched between twointernal electrode layers was 500. Evaluation was made in the same wayas in the Example 1.

As a result, the static capacitance of the obtained capacitor sampleswas 74 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 50%. The shape anisotropy of the capacitor sampleswas “∘” and no shape anisotropy was observed.

EXAMPLE 5

Capacitor samples were obtained in the same way as in the Example 2except that the number of dielectric layers sandwiched between twointernal electrode layers was 500. Evaluation was made in the same wayas in the Example 2.

As a result, the static capacitance of the obtained capacitor sampleswas 80 μF and the capacity was confirmed to be increased comparing withthat of the Example 4. The defective fraction of insulation resistance(IR) of the capacitor samples was 0% and the IR defective fraction wasconfirmed to be drastically improved comparing with the Example 4. Theshape anisotropy of the capacitor samples was “∘” and no shapeanisotropy was observed.

EXAMPLE 6

Capacitor samples were obtained in the same way as in the Example 3except that the number of dielectric layers sandwiched between twointernal electrode layers was 500. Evaluation was made in the same wayas in the Example 3.

As a result, the static capacitance of the obtained capacitor sampleswas 78 μF and the capacity was increased comparing with that of theExample 4. While, a little decrease in capacity was confirmed comparingwith the Example 5. It is deemed that it is because when hydrogenintroduction starts at the time of reaching the firing temperature,sintering of the dielectrics tends to be insufficient, and thereby, thecapacity decreases. The defective fraction of insulation resistance (IR)of the capacitor samples was 0% and the IR defective fraction wasconfirmed to be drastically improved comparing with the Example 4. Theshape anisotropy of the capacitor samples was “∘” and no shapeanisotropy was observed.

COMPARATIVE EXAMPLE 3

Capacitor samples were obtained in the same way as in the ComparativeExample 1 except that the number of dielectric layers sandwiched betweentwo internal electrode layers was 500. Evaluation was made in the sameway as in the Comparative Example 1.

As a result, the static capacitance of the obtained capacitor sampleswas 62 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 100%. The shape anisotropy of the capacitorsamples was “x”. The respective evaluations were inferior to those ofthe Examples 4 to 6, and superiority of the Examples 4 to 6 wasconfirmed.

COMPARATIVE EXAMPLE 4

Capacitor samples were obtained in the same way as in the ComparativeExample 2 except that the number of dielectric layers sandwiched betweentwo internal electrode layers was 500. Evaluation was made in the sameway as in the Comparative Example 2.

As a result, the static capacitance of the obtained capacitor sampleswas 62 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 100%. The shape anisotropy of the capacitorsamples was “x”. The respective evaluations were inferior to those ofthe Examples 4 to 6, and superiority of the Examples 4 to 6 wasconfirmed.

EXAMPLE 7

The number of dielectric layers sandwiched between two internalelectrode layers was 500. Hydrogen introduction was stopped at the timethe temperature was lowered to 1100° C. in the temperature lowering stepin the firing step, the atmosphere was changed to a wet nitrogen gas(oxygen partial pressure was 10⁻¹ Pa or so) and the temperature waslowered to the room temperature (25° C.). Furthermore, annealing was notperformed. Except for the above, capacitor samples were obtained in thesame way as in the Example 6. Evaluation was made in the same way as inthe Example 6.

As a result, the static capacitance of the obtained capacitor sampleswas 80 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 0%. The shape anisotropy of the capacitor sampleswas “∘” and no shape anisotropy was observed.

EXAMPLE 8

First, the temperature was raised from the room temperature (25° C.) to1150° C. at a temperature raising rate of 200° C./hour under anatmosphere gas using a wet nitrogen gas (oxygen partial pressure was10⁻¹ Pa or so), kept for 60 minutes, and then lowered to the roomtemperature (25° C.). After that, hydrogen introduction was started andthe atmosphere was changed to a mixed gas of a wet nitrogen and hydrogen(5 percent by volume of H₂). The temperature was raised to the firingtemperature of 1220° C. at a temperature raising rate of 200° C./hourunder the atmosphere. Then, after performing firing by holding thefiring temperature of 1220° C. for 2 hours without changing theatmosphere, the temperature was lowered to the room temperature (25° C.)at a temperature lowering rate of 200° C./hour. Except for the above,capacitor samples were obtained in the same way as in the Example 1.

As a result, the static capacitance of the obtained capacitor sampleswas 14 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 0%. The shape anisotropy of the capacitor sampleswas “∘” and no shape anisotropy was observed.

Note that the Example 8 is accordingly the same as the ComparativeExample 1 in a point that hydrogen is introduced from the roomtemperature (25° C.), but different from the Comparative Example 1 inpoints that the static capacitance, IR defective fraction and shapeanisotropy are all preferable. The reason is not exactly clear but it isdeemed that it is because by raising the temperature once to apredetermined temperature without introducing hydrogen, oxidization ofthe internal electrodes progresses and sintering of the dielectricsprogresses.

EXAMPLE 9

The temperature was held at the temperature of starting the hydrogenintroduction (1150° C.) for 30 minutes and raised to the firingtemperature of 1220° C. Then, after performing firing by holding thefiring temperature of 1220° C. for 2 hours without changing theatmosphere, the temperature was lowered to the room temperature (25° C.)at a temperature lowering rate of 200° C./hour. Except for the above,capacitor samples were obtained in the same way as in the Example 2.Evaluation was made in the same way as in the Example 2.

As a result, the static capacitance of the obtained capacitor sampleswas 14 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 0%. The shape anisotropy of the capacitor sampleswas “∘” and no shape anisotropy was observed.

EXAMPLE 10

Capacity samples were obtained in the same way as in the Example 1except for starting the hydrogen introduction at 1150° C. by usingconcentration gradient of attaining 5 percent by volume (oxygen partialpressure was 10⁻⁸ Pa or so) at the time that a temperature is 1220° C.Evaluation was made in the same way as in the Example 1.

As a result, the static capacitance of the obtained capacitor sampleswas 15 μF. The defective fraction of insulation resistance (IR) of thecapacitor samples was 0%. The shape anisotropy of the capacitor sampleswas “∘” and no shape anisotropy was observed.

The results are listed in Table 1.

hydrogen number of introduction stacked layers in static capacitance IRdefective shape temperature ° C. dielectric layers μm fractionanisotropy Example 1 1100 100 13 50 ∘ Example 2 1150 100 15 0 ∘ Example3 1220 100 14 0 ∘ Comparative Example 1  25 100 11 95 x ComparativeExample 2  800 100 11 95 x Example 4 1100 500 74 50 ∘ Example 5 1150 50080 0 ∘ Example 6 1220 500 78 0 ∘ Comparative Example 3  25 500 62 100 xComparative Example 4  800 500 62 100 x Example 7  1220* 500 80 0 ∘Example 8  25 100 14 0 ∘ Example 9 1150 100 14 0 ∘ Example 10 1150 10015 0 ∘ *hydrogen introduction was stopped when the temperature islowered to 1100° C.

EXAMPLE 11

As starting materials, a dielectric material obtained by mixing so as tobe a composition of 100 mole % as BaTiO₃ (Ba/Ti=1.000), 1.0 mole % asY₂O₃, 2.0 mole % in a conversion of (Ba_(0.58)Ca_(0.42))SiO₃, 0.2 mole %in a conversion of Cr₂O₃, 1.8 mole % in a conversion of MgO, 0.06 mole %in a conversion of V₂O₅, performing wet mixing by a ball mill for 16hours and drying was used.

Then, capacitor samples were obtained in the same procedure andconditions as in the Example 1 except that the hydrogen introductiontemperature was 1150° C., the firing temperature was 1280° C. for 2hours, the thickness of the dielectric layer green sheet was 5 μm andthe number of stacked layers in the sheet was 280.

The obtained capacitor samples had a size of 3.2 mm×1.6 mm×0.6 mm, thenumber of dielectric layers sandwiched between two internal electrodelayers was 280 and a thickness thereof was 3 μm.

Sections of the capacitor samples were polished, observed by an opticalmicroscope, and the thickness of the internal electrode layer wasmeasured by using a micrometer. The result was that the thickness of theinternal electrode layer was about 1.05 μm and an increase of athickness in the stacking direction was suppressed.

EXAMPLE 12

Capacitor samples were obtained in the same procedure and conditions asin the Example 11 except for changing the hydrogen introductiontemperature to 1200° C. Evaluation was made in the same way as in theExample 11. The result was that the thickness of the internal electrodewas about 1.08 μm and an increase of a thickness in the stackingdirection was suppressed.

COMPARATIVE EXAMPLE 5

Capacitor samples were obtained in the same procedure and conditions asin the Example 11 except for changing the hydrogen introductiontemperature to the room temperature (25° C.) as in the ComparativeExample 1. Evaluation was made in the same way as in the Example 11. Theresult was that the thickness of the internal electrode was about 1.32μm and an increase of a thickness in the stacking direction was notsuppressed. Superiority of the Examples 11 and 12 in this point wasconfirmed.

The results are listed in Table 2.

TABLE 2 thickness of internal hydrogen introduction electrode layerstemperature ° C. after firing μm Example 11 1150 1.05 Example 12 12001.08 Comparative Example 5 25 1.32

EXAMPLE 13

A dielectric layer paste was prepared as described below.

First, powders of CaZrO₃, SrZrO₃, CaTiO₃, MnCO₃, Al₂O₃, BaCO₃, CaCO₃ andSiO₂ were prepared as materials. The powders were mixed so as to be acomposition of 100 mole % as a composition formula{(Ca_(0.7)Sr_(0.3))O}(Ti_(0.03)ZrO_(0.97))O₂, 1 mole % in a conversionof MnO, 0.2 mole % in a conversion of Al₂O₃ and 2.8 mole % as{(Ba₀₆Ca₀₄)O}SiO₂, subjected to wet mixing by a ball mill for 16 hoursand dried by a spray drier to obtain a dielectric material. Then, 100parts by weight of the obtained dielectric material, 5.4 parts by weightof an acrylic resin, 45 parts by weight of methylene chloride, 16 partsby weight of ethyl acetate, 6 parts by weight of mineral spirits and 4parts by weight of acetone were mixed by a ball mill to obtain a paste.

An internal electrode paste was prepared as described below.

A paste was obtained by kneading using a triple-roll 100 parts by weightof Ni particle having an average particle diameter of 0.8 μm, 35 partsby weight of organic vehicle (8 parts by weight of an ethyl celluloseresin was dissolved in 92 parts by weight of butyl carbitol) and 7 partsby weight of butyl carbitol.

Next, an external electrode paste was prepared as described below. Apaste was obtained by kneading 100 parts by weight of Cu particle havingan average particle diameter of 0.5 μm, 35 parts by weight of organicvehicle (8 parts by weight of an ethyl cellulose resin is dissolved in92 parts by weight of butyl carbitol) and 7 parts by weight of butylcarbitol.

Next, the above dielectric layer paste was used for forming a greensheet of a thickness of 6.5 μm on a PET film, the internal electrodepaste was printed by a predetermined pattern thereon, and then, thegreen sheet was removed from the PET film.

Next, a plurality of the green sheets and protective green sheets (onwhich the internal electrode paste is not printed) were stacked andpressured to obtain a green stacked layer body. The number of stackedlayers in the sheet having the internal electrodes were 330.

Then, the green stacked layer body was cut to a predetermined size toobtain a green chip, on which a binder removing step and firing stepwere performed to obtain a chip sintered body.

The binder removing processing was performed under conditions below.

-   -   temperature raising time: 15° C./hour    -   holding temperature: 260° C.    -   holding time: 8 hours    -   atmosphere: in the air

Firing was performed under conditions below.

First, the temperature was raised from the room temperature (25° C.) to1050° C. at a temperature raising rate of 300° C./hour under anatmosphere gas using a wet nitrogen gas (an oxygen partial pressure was10⁻² to 1 Pa or so). A wetter with a water temperature of 20° C. wasused for wetting the atmosphere gas. Then, hydrogen introduction wasstarted at 1050° C. to change the atmosphere to a mixed gas of a wetnitrogen gas and hydrogen gas (5 percent by volume of H₂, and the oxygenpartial pressure was 10⁻⁶ Pa or so). The temperature was raised to thefiring temperature of 1325° C. under the atmosphere.

Next, firing was performed by holding the firing temperature of 1325° C.for 2 hours without changing the atmosphere.

Then, the temperature was lowered to the room temperature (25° C.) at atemperature lowering rate of 300° C./hour without changing theatmosphere.

Next, end surfaces of the obtained chip sintered body were barrelpolished, the above external electrode paste was transferred on the chipend surfaces, firing was performed at 800° C. for 30 minutes under a wetnitrogen gas atmosphere to form external electrodes, and multilayerceramic capacitor samples having a configuration shown in FIG. 1 wereobtained.

The obtained capacitor samples had a size of 4.5 mm×3.2 mm×2.3 mm,wherein the number of dielectric layers sandwiched between two internalelectrode layers was 330, a thickness thereof was 4 μm and the thicknessof the internal electrode layer was 1.7 μm.

A crack occurrence rate of the obtained capacitor samples was evaluated.

The crack occurrence rate (%) was calculated as below. First, anappearance of 200 capacitor samples was observed by using an opticalmicroscope (UFX-II made by Nikon Corporation) to confirm an existence ofa crack and 30 capacitor samples not having any cracks were selected.Then, the 30 capacitor samples were buried a resin, polished by 2 mm inthe direction of the lengthwise of 4.5 mm and examined an existence ofan internal crack by an optical microscope, and the number of capacitorsamples wherein an internal crack occurred was divided by the wholequantity (30) for indicating by percentage. As a result, the crackoccurrence was 86.7%.

EXAMPLE 14

Capacitor samples were obtained in the same way as in the Example 13except that hydrogen introduction was started at the time thetemperature was raised to 1100° C., the atmosphere was changed to amixed gas of a wet nitrogen gas and hydrogen gas, and the temperaturewas raised to the firing temperature of 1325° C. under the atmosphere inthe firing step. A size, the number of dielectric layers and a thicknessthereof, and the thickness of an internal electrode layer were the sameas those in the Example 13. Then, evaluation was made in the same way asin the Example 13. As a result, the crack occurrence rate of theobtained capacitor samples was 56.7%.

EXAMPLE 15

Capacitor samples were obtained in the same way as in the Example 13except that hydrogen introduction was started at the time thetemperature was raised to 1150° C., the atmosphere was changed to amixed gas of a wet nitrogen gas and hydrogen gas, and the temperaturewas raised to the firing temperature of 1325° C. under the atmosphere inthe firing step. Then, evaluation was made in the same way as in theExample 13. A size, the number of dielectric layers and a thicknessthereof, and the thickness of an internal electrode layer were the sameas those in the Example 13. As a result, the crack occurrence rate ofthe obtained capacitor samples was 3.3%.

EXAMPLE 16

Capacitor samples were obtained in the same way as in the Example 13except that hydrogen introduction was started at the time thetemperature was raised to 1200° C., the atmosphere was changed to amixed gas of a wet nitrogen gas and hydrogen gas, and the temperaturewas raised to the firing temperature of 1325° C. under the atmosphere inthe firing step. A size, the number of dielectric layers and a thicknessthereof, and the thickness of an internal electrode layer were the sameas those in the Example 13. Then, evaluation was made in the same way asin the Example 13. As a result, the crack occurrence rate of theobtained capacitor samples was 0%.

EXAMPLE 17

Capacitor samples were obtained in the same way as in the Example 13except that hydrogen introduction was started at the time thetemperature was raised to 1250° C., the atmosphere was changed to amixed gas of a wet nitrogen gas and hydrogen gas, and the temperaturewas raised to the firing temperature of 1325° C. under the atmosphere inthe firing step. A size, the number of dielectric layers and a thicknessthereof, and the thickness of an internal electrode layer were the sameas those in the Example 13. Then, evaluation was made in the same way asin the Example 13. As a result, the crack occurrence rate of theobtained capacitor samples was 0%.

EXAMPLE 18

Capacitor samples were obtained in the same way as in the Example 13except that hydrogen introduction was started at the time thetemperature was raised to 1280° C., the atmosphere was changed to amixed gas of a wet nitrogen gas and hydrogen gas, and the temperaturewas raised to the firing temperature of 1325° C. under the atmosphere inthe firing step. A size, the number of dielectric layers and a thicknessthereof, and the thickness of an internal electrode layer were the sameas those in the Example 13. Then, evaluation was made in the same way asin the Example 13. As a result, the crack occurrence rate of theobtained capacitor samples was 3.3%.

EXAMPLE 19

Capacitor samples were obtained in the same way as in the Example 13except that hydrogen introduction was started at the time thetemperature was raised to 1325° C., the atmosphere was changed to amixed gas of a wet nitrogen gas and hydrogen gas, and the firingtemperature was 1325° C. under the atmosphere in the firing step. Asize, the number of dielectric layers and a thickness thereof, and thethickness of an internal electrode layer were the same as those in theExample 13. Then, evaluation was made in the same way as in the Example13. As a result, the crack occurrence rate of the obtained capacitorsamples was 0%.

COMPARATIVE EXAMPLE 6

Capacitor samples were obtained in the same way as in the Example 13except that hydrogen introduction was started at the time thetemperature was raised to 800° C., the atmosphere was changed to a mixedgas of a wet nitrogen gas and hydrogen gas, and the temperature wasraised to the firing temperature of 1325° C. under the atmosphere in thefiring step. A size, the number of dielectric layers and a thicknessthereof, and the thickness of an internal electrode layer were the sameas those in the Example 13. Then, evaluation was made in the same way asin the Example 13. As a result, the crack occurrence rate of theobtained capacitor samples was 100%. Thereby, superiority of theExamples 13 to 19 was confirmed.

COMPARATIVE EXAMPLE 7

Capacitor samples were obtained in the same way as in the Example 13except that hydrogen introduction was started from the beginning oftemperature raising at the room temperature (25° C.), the atmosphere waschanged to a mixed gas of a wet nitrogen gas and hydrogen gas, and thetemperature was raised to the firing temperature of 1325° C. under theatmosphere in the firing step. A size, the number of dielectric layersand a thickness thereof, and the thickness of an internal electrodelayer were the same as those in the Example 13. Then, evaluation wasmade in the same way as in the Example 13. As a result, the crackoccurrence rate of the obtained capacitor samples was 100%. Thereby,superiority of the Examples 13 to 19 was confirmed.

The results are shown in Table 3 and FIG. 2.

TABLE 3 number of hydrogen stacked layers crack introduction indielectric occurrence rate temperature ° C. layers % Example 13 1050 33086.7 Example 14 110 330 56.7 Example 15 1150 330 3.3 Example 16 1200 3300 Example 17 1250 330 0 Example 18 1280 330 3.3 Example 19 1325 330 0Comparative 800 330 100 Example 6 Comparative 25 330 100 Example 7Example 20 25 330 0

From Table 3 and FIG. 2, in the case where the temperature of binderremoving was 260° C. and the thickness of the green sheet was 6.2 μm, anoccurrence of cracks started to be suppressed by setting the temperatureof starting hydrogen introduction at more than 800° C. and wasremarkably prevented by setting the temperature at more than 1050° C.

EXAMPLE 20

First, the temperature was raised from the room temperature (25° C.) to1200° C. at a temperature raising rate of 300° C./hour under anatmosphere gas using a wet nitrogen gas (oxygen partial pressure was10⁻¹ Pa or so), kept for 3 minutes, and then lowered to the roomtemperature (25° C.). After that, hydrogen introduction was started andthe atmosphere was changed to a mixed gas of a wet nitrogen gas andhydrogen gas (5 percent by volume of H₂). The temperature was raised tothe firing temperature of 1325° C. at a temperature raising rate of 300°C./hour under the atmosphere. Then, after performing firing by holdingthe firing temperature of 1325° C. for 2 hours without changing theatmosphere, the temperature was lowered to the room temperature (25° C.)at a temperature lowering rate of 300° C./hour. Except for the above,capacitor samples were obtained in the same way as in the Example 13. Asize, the number of dielectric layers and a thickness thereof, and thethickness of an internal electrode layer were the same as those in theExample 13. Then, evaluation was made in the same way as in the Example13. As a result, the crack occurrence rate of the obtained capacitorsamples was 0%.

1. A method of producing a multilayer ceramic electronic device, havinga firing step for firing a pre-firing element body wherein a pluralityof dielectric layers and internal electrode layers containing a basemetal are alternately arranged, characterized in that: said firing stephas a temperature raising step for raising a temperature to a firingtemperature; hydrogen is continued to be introduced from a point in timeof said temperature raising step, wherein a temperature for initiallyintroducing said hydrogen is 1000° C. or more; and said dielectric layerhas a main component containing BaTiO₃.
 2. The method of producing amultilayer ceramic electronic device as set forth in claim 1, whereinthe hydrogen is introduced after the base metal contained in theinternal electrode is oxidized, to reduce the oxidized metal.
 3. Amethod of producing a multilayer ceramic electronic device, having afiring step for firing a pre-firing element body wherein a plurality ofdielectric layers and internal electrode layers containing a base metalare alternately arranged, characterized in that: said firing step has atemperature raising step for raising a temperature to a firingtemperature; hydrogen is continued to be introduced from a point in timeof said temperature raising step, wherein a temperature for initiallyintroducing said hydrogen is 1000° C. or more; and said dielectric layerhas a main component containing (BaCa) (TiZr)O₃.
 4. The method ofproducing a multilayer ceramic electronic device as set forth in claim3, wherein the hydrogen is introduced after the base metal contained inthe internal electrode is oxidized, to reduce the oxidized metal.
 5. Amethod of producing a multilayer ceramic electronic device, having afiring step for firing a pre-firing element body wherein a plurality ofdielectric layers and internal electrode layers containing a base metalare alternately arranged, characterized in that: said firing step has atemperature raising step for raising a temperature to a firingtemperature; hydrogen is continued to be introduced from a point in timeof said temperature raising step, wherein a temperature for initiallyintroducing said hydrogen is 1000° C. or more; and said dielectric layerhas a main component containing a dielectric oxide indicated by acomposition formula ((Ba_(1-x)Ca_(x))O)_(m)(Ti_(1-z)Zr_(z))O₂ wherein0≦x≦0.25, 0≦z≦0.30, 1.000≦m≦1.020; and said multilayer ceramicelectronic device is a multilayer ceramic capacitor.
 6. The method ofproducing a multilayer ceramic electronic device as set forth in claim5, wherein the hydrogen is introduced after the base metal contained inthe internal electrode is oxidized, to reduce the oxidized metal.
 7. Amethod of producing a multilayer ceramic electronic device, having afiring step for firing a pre-firing element body wherein a plurality ofdielectric layers and internal electrode layers containing a base metalare alternately arranged, characterized in that: said firing step has atemperature raising step for raising a temperature to a firingtemperature; hydrogen is continued to be introduced from a point in timeof said temperature raising step, wherein a temperature for initiallyintroducing said hydrogen is 1000° C. or more; and said dielectric layerhas a main component containing a dielectric oxide indicated by acomposition formula Ba_(m)TiO₃ wherein 0.95<m<1.01; and said multilayerceramic electronic device is a multilayer ceramic capacitor.
 8. Themethod of producing a multilayer ceramic electronic device as set forthin claim 7, wherein the hydrogen is introduced after the base metalcontained in the internal electrode is oxidized, to reduce the oxidizedmetal.